1. Field of the Invention
The present invention relates generally to fuel vapor emission control for internal combustion engines. More particularly, the present invention relates fuel tank fuel vapor emission control for internal combustion engines.
2. Description of the Related Art
Modern transportation vehicles which employ a liquid fuel conventionally also employ for storage of the liquid fuel a fuel tank. Similarly, since most liquid fuels are highly volatile, such a fuel tank typically contains in addition to the liquid fuel a fuel vapor. A concentration of fuel in the fuel vapor within the fuel tank is generally related to a temperature of the liquid fuel and the fuel vapor.
While a fuel vapor within a fuel tank does not typically impair operation of a transportation vehicle powered by an engine which employs a liquid fuel extracted from the fuel tank, upon refueling of the fuel tank with additional liquid fuel the fuel vapor must of necessity be displaced. For environmental protection purposes and for economic reasons, it is desirable for such displaced fuel vapor not to be released into the atmosphere.
Various apparatus, systems and methods have been disclosed within the arts of both fuel tank design and fuel system design for attenuating upon refueling of a fuel tank release of a fuel vapor into the atmosphere. Well known in this regard is the use of carbon filled canisters for cyclical absorptive capture and desorptive controlled release of fuel vapors displaced incident to refueling of a fuel tank.
Similarly, also known in the art are various apparatus, systems and methods which are predicated upon thermally induced condensation of a fuel vapor, such as a displaced fuel vapor, to provide a liquid fuel which is returned to a fuel tank. Representative disclosures directed towards such condensation of fuel vapor may be found within U.S. Pat. Nos. 4,671,071, 5,255,735 and 5,957,113.
While any of the foregoing apparatus, systems and methods provides upon refueling of a fuel tank with a liquid fuel attenuated displaced fuel vapor release into the atmosphere, such desirable result is often achieved only with complicated piping and valving schemes, or with electrical system drain upon an engine which is powered by the liquid fuel which forms the fuel vapor.
There thus exists within the art of fuel tank design and fuel system design a continuing need for comparatively simple apparatus, systems and methods for avoiding upon refueling of a fuel tank release of a displaced fuel vapor to the atmosphere. It is towards that object that the present invention is directed.